A basic centrifugal pump is not self-priming, and various self-priming centrifugal pumps have been developed.
Most commonly, a self-priming centrifugal pump is provided with a discharge tank contained in the pump housing and connected to recirculate liquid through the pumping chamber for priming. These tanks are initially provided with a supply of the liquid to be pumped and, during priming, the pump impeller is rotatably driven to recirculate liquid from the tank through the pumping chamber, so that gas in the pumping chamber becomes entrained with the recirculated liquid.
In other designs, an additional external pump is provided simply for priming, for example a liquid piston pump functioning as a priming wheel.
There is still a need for a self-priming centrifugal pump in which the priming arrangement takes up a small amount of space and also does not reduce significantly the efficiency of the pump.